1. Field of the Invention
This invention relates to dosage forms for administration of drugs and more particularly to buccal dosage forms having a polymeric matrix for controlled release of a drug.
2. Description of the Prior Art
Administration of drugs by absorption through the oral mucosa has been found to be an efficient and convenient method of supplying to the body a drug which is not well adapted to administration via the intestinal route. Some drugs are poorly absorbed from the gastrointestinal tract; others are rapidly metabolized in the liver and do not reach the target organ. Transmucosal administration, which introduces the drug directly into the bloodstream, avoids the problems of poor absorption or rapid metabolism.
However, because the continuous secretion of saliva rapidly washes dissolved drugs out of the oral cavity, sublingual and buccal administration of drugs have been most useful for drugs, such as nitroglycerin, which are very rapidly absorbed through the oral mucosa. In order to keep a drug in contact with the oral mucosa for a longer period of time, sustained release dosage forms especially adapted for transmucosal administration of drugs have been developed. These have generally comprised a drug dispersed in a matrix which slowly releases the drug by diffusion from the matrix or by slow dissolution or erosion of the matrix. In order to retain the dosage form within the mouth, it may be bonded to an adhesive patch or the dosage form itself may be provided with an adhesive layer which adheres to the mucosa. Alternatively, the dosage form itself may adhere to the mucosa and slowly dissolve, releasing the drug contained therein.
For example, Zaffaroni, U.S. Pat. No. 3,598,122, discloses an adhesive buccal device having an impermeable backing layer and a drug-containing adhesive matrix layer which adheres to the oral mucosa, allowing the drug to diffuse through the mucosa over a period of time. This device has the drawback that it must be removed from the mouth after the drug has been dispensed.
Another adherent dosage form comprising an impervious backing material coated with an adhesive which adheres to the mucosa and having a drug reservoir matrix comprised of a mixture of low molecular weight polyethylene glycol and polyvinylpyrrolidone is disclosed in Tsuk, U.S. Pat. No. 3,972,995. Evidently this dosage form suffers from the same problems as that of Zaffaroni.
Another approach is exemplified by Nagai, U.S. Pat. No. 4,250,163, who discloses a totally soluble adhesive buccal dosage form which adheres to the oral mucosa and releases the medication over a period of 10-40 minutes. The dosage form is a lamella having the drug dispersed in a matrix comprised of 50-95% of a cellulose ether and 5-50% of an acrylic polymer. These dosage forms are prepared by compression molding of a mixture of ingredients in powder form, which sometimes presents problems in obtaining uniform distribution of the drug in the matrix.
A buccal dosage form comprising a strip of gauze or paper impregnated with a drug in a matrix of a mixture of polyethylene glycols is disclosed in Applezweig, U.S. Pat. No. 3,536,809. This dosage form also has the drawback that the supporting gauze or paper must be removed from the mouth after the medicine has been exhausted.
DeFoney, in U.S. Pat. Nos. 3,911,099 and 4,039,653, discloses a dosage form comprising a tablet or similar article formed of a sustained release matrix of polyvinylpyrrolidone containing an odor masking substance which is retained in the oral cavity by means of an adhesive layer on one side of the tablet.
Hence a need has continued to exist for a buccal dosage form which adheres to the oral mucosa, provides for administration of medication over a controlled period of time, has a very uniform distribution of the drug in the matrix, and which completely dissolves in the mouth.